Recent evidence suggests that CD8+ T-lymphocytes of the Vb 3 or Vb 13.1 subsets are activated and clonally expanded in skin lesions of psoriasis vulgaris. This study is a clinical and pathological examination of potential disease-mediating functions of these T-cell subsets. The study involves administration of a bivalent peptide vaccine containing epitopes from Vb 3 and Vb 13.1 constant regions to patients with chronic psoriasis vulgaris. Part A of the study is concerned with clinical evaluation of outcomes. Part B of the study is concerned with assessment of T- lymphocyte subsets in psoriatic skin lesions before and during treatment, as assessed in skin biopsies.